ACI Concrete Field Testing Technician - Grade I Practice Exam

How many layers should the concrete sample be filled in when consolidating by vibration?

1. 1 equal

2. 2 equal

3. 3 equal

4. 4 equal

The correct answer is: 2 equal

When consolidating a concrete sample by vibration, it is essential to fill the sample in multiple layers to ensure uniform compaction and minimize the risk of voids. The best practice is to use two equal layers for most standard tests. By filling the sample in this manner, the concrete can be effectively compacted, allowing vibratory energy to reach all parts of the sample, thus helping to eliminate air pockets and achieve a uniform density throughout the entire specimen. Two layers allow for adequate control over the consolidation process, ensuring that the vibrational energy is appropriately applied to each layer. This method ensures that the concrete is effectively worked into the mold without excessive segregation or the trapping of air, both of which could negatively impact the integrity and performance characteristics of the concrete being tested. Filling the sample in fewer layers may not provide enough surface area for effective compaction, while using more than two layers can lead to complications in achieving uniformity, as the lower layers may start to set or harden before the top layers are compacted. Hence, the practice of filling the sample in two equal layers strikes the best balance between effective consolidation and practical execution in the field.